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SBIR/STTR

High Input Voltage Hall Thruster Discharge Converter, Phase I

Project Introduction

The overall scope of this Phase I/II effort is the development of a high efficiency 15kW (nominal) Hall thruster discharge converter. In Phase I, Busek Co. Inc. will design, fabricate and test a nominal 7.5kW breadboard discharge converter module. Busek proposes a converter topolgy called the Leading Edge Auxiliary Phase Shifted (LEAPS) Bridge, which is a modification of the standard phase shifted bridge that uses an energy-recovering auxiliary circuit to force the transition from output inductor freewheel to power flowing through the main transformer. Based on preliminary measurements with this topology the converter module demonstrated >97% efficiency at reduced power. A 300V line input and 300-400V output range are the benchmark for the discharge converter in Phase 1. The most reasonable path with higher input voltage for higher power converters involves the use Wide Band Gap FETs. MOSFETS represent the greatest payoff in terms of efficiency improvements and are a primary focus for a discharge converter to achieve an efficiency of 98% or greater. With the design maturity gained from the Phase I breadboard, the Phase II objective will be the production of a 15kW brassboard PPU in a flight-like form factor that incorporates conductive cooling.
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Anticipated Benefits

NASA has identified 30kW-class SEP systems as a high-value intermediate step toward higher power systems due to broad cross-cutting capability. Current NASA investments include advanced next-generation solar arrays and higher power electric propulsion technologies to enable 30kW-class SEP. The ESPA ring is one approach being considered for partner-based mission concepts and those capable of being launched as secondary payloads. In addition NASA is investing in EP development of 15kW class HET system using either direct-drive and/or high voltage power processing unit. The possibility for using Hall thrusters for lunar and Mars missions has also been well investigated. Hall thrusters have been found to be a good choice for Mars cargo missions and other studies have found Hall thrusters to be viable options for supporting lunar and Mars exploration. Another NASA study indicates that a cluster of eight 100 kW Hall thrusters would be well sized for manned Mars missions.
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